The invention relates to a constructed piston comprising an upper part produced from steel and a lower part produced from an iron material, as defined in the introductory part claim 1, or to a piston made of iron material that is comprised of at least two components that are joined with one another by welding or soldering techniques.
With the pistons produced from iron material as they are known heretofore, the lower part or the entire piston is made of cast iron, as a rule.
Furthermore, a piston is known from DE 30 32 671 A in connection with which the upper part of the piston consists of heat-resistant steel and the lower part of the piston of flow-pressed steel, and the upper and lower parts of the piston are joined with one another by welding or soldering. Said piston, however, has remained the state of the art on paper only.
More recent constructions dispense with the use of cast iron materials and, in selecting the material for iron pistons or for the lower parts of pistons, have changed to forged steel because casting defects, which never can be totally excluded, may lead to damage in connection with increased ignition pressures.
However, forged lower parts and pistons produced in the form of one single part from forged steel, pose the problem that the manufacture of long shafts is difficult in terms of forging technology. The forgeability of a component depends on the depth to which the forging die is pressed in, and upon the taper slants. The required taper slants, on the other hand, led to unnecessarily high thickness of the wall of the shaft. In order to avoid this, the lower edge of the shaft is provided with a relatively thin wall. This leads to the fact that the end of the shaft tends to vibrate as it is being worked.